Architecture Diagramming Standard

Priority: P1 (HIGH)

Pipeline

Never hand-write mxGraph XML. Write a spec; the scripts own every visual decision, so diagrams stay identical across authors, repositories, and sessions.

1. Write spec.json — schema in diagram-spec.md. For an ERD, generate it: python3 scripts/schema_to_spec.py db/schema.sql --title "<System> — ERD" -o spec.json
2. python3 scripts/validate_spec.py spec.json
3. python3 scripts/render_drawio.py spec.json -o docs/architecture/<slug>.drawio --strict (exit 2 = a layout finding; change the spec, per layout-rules.md)
4. For related views, optionally validate view-manifest.md: python3 scripts/validate_manifest.py view-manifest.json
5. Export the image: a draw.io MCP tool if the session has one, else python3 scripts/export_drawio.py docs/architecture/<slug>.drawio -f png -o docs/architecture/<slug>.png, else ship the .drawio and say the image was not exported. See export paths.
6. Inspect the exported image at normal reading size; strict validation cannot prove labels and edges are legible. Fix the spec and re-export before handoff.

The JSON spec is the semantic source of truth; .drawio is the editable presentation and the image is a copy for a deck. Generated XML records its own baseline; regeneration protects manual edits by default. Use --acknowledge-manual-edits only after returning semantic changes to the spec.

Guidelines

• Name the audience and the decision before drawing anything.
• One C4 level per diagram: context, container, or component, never mixed.
• Pick the type from the message, not from habit. See diagram-selection.md.
• Evidence and confidence are separate. Code citations are documented evidence, not runtime observations; use assumed or unverified for honest design uncertainty.
• Put the number on the box. metric carries the load or SLO that sized the node, constraint says why it exists; never invent either.
• Label every edge with its protocol or event; use style: async for events.
• Cloud icons only where verified. gcp:* and aws:* are official icons; every other vendor is a cloud:* kind with the service named in sublabel. No Azure logos exist in the bundle, so Azure is always cloud:*.
• Exec audience caps at 12 nodes. Past that, split by level or by flow.
• Legend and title block are generated. Do not remove or duplicate them.
• Refine in the spec, not by mutating generated XML. Regeneration preserves files with a valid own baseline, but refuses hand mutation until explicitly acknowledged.

Anti-Patterns

• No hand-written XML: Write the spec, run the renderer.
• No invented boxes: Omit what the evidence does not support.
• No mixed levels: Table columns never appear in a context diagram.
• No unlabeled arrows: State the protocol or the event.
• No mystery acronyms: Expand every abbreviation on first use.
• No orphan nodes: Connect it or cut it.

Red Flags

Thought	Reality
"It is one box, I will write the XML"	The renderer owns style, legend, and title block. Use it.
"Close enough, I will guess this service"	Guesses ship as facts. Omit the evidence and let it render UNVERIFIED.
"Managers want the whole system on one page"	Past 12 nodes they stop reading. Split it.

References

• Diagram spec · View manifest · Style catalog · House style
• Source extraction · Exec readability
• C4 model · Cloud · Best practices
• Layout rules · Checklist · Export paths and Mermaid fallback
• Runnable examples: assets/fixtures/<type>.spec.json, one per diagram type, plus schema samples under assets/fixtures/schemas/.
• Batch or delegated drawing: specialist-solution-diagrammer.